Cell Signaling Flashcards
What are the three main stages of cell signaling
Reception
Transduction
Response
Reception
A signaling molecule binds to a protein receptor and make it do things
The receptor can be on the plasma membrane or inside the cell
Transduction
A series of relay molecules that carries the signal into the cell and amplifies the signal
Response
This goes on inside the cell and activates cellular response
Ligand
This is a small molecule that binds. The binding is capable of producing a signal.
**These are signaling molecules
The ligand will only bind and activate one specific receptor protein. True/ False
True
List the three general class of receptors
G protein-coupled receptors
Receptor tyrosine Kinases
Ion channel receptors
Receptors inside the cell(cytoplasmic) do not responds\ to the membrane-permeable(small and hydrphobic) signals of the cell. True/False
False
G protein-coupled receptors (GPCR)
It has 7 transmembrane domains
When a signaling molecule binds with a GPCR this cause a conformational change in the GPCR.
This change can trigger a reaction with the GPCR and a G protein
G protein
This is a membrane bound enzyme that is part of the signal transduction system
G protein can be bound to the GDP(off site) or GTP (on site)
Steps to activate G protein
- Ligand binds to the GPCR, the receptor changes shape
- This allows the G protein to dock it
- GDP is released and GTP is loaded in. This activates the g protein
What happens to the activated G protein
- The activated g protein binds an inactive enzyme and activate it
- The enzyme can usually make cyclic AMP (cAMP - Cyclic Adenosine Monophosphate)
3 This can initiate the signal transduction
What happens when GTP is hydrolyzed?
When GTP is hydrolyzed, it releases phosphate and turns to GDP
Rhodopsin
one of a few GPCR in rod cell(a type of photoreceptors) that make up your eyes
Retinal
a small molecule cofactor (non protein or metallic compound that helps the enzyme catalyze reaction) that is bound to the receptor.
A retinal absorbs an incoming photon of light. True/False
True. This causes the retinal to go from cis to trans conformation, the GCPR changes shape and start signal transduction
When a ligand binds to a receptor tyrosine kinases what happens?
The receptor (single alpha helixes) comes together to form dimer.
**they were separate before.
Kinase
An enzyme that can add a phosphate group onto something(other molecules)
How is the receptor activated in receptor tyrosine kinases?
It is activated when the two monomers add phosphate to the hydroxyl group on the R groups of the tyrosine
Does the phosphorylated tyrosines act as docking sites for relay proteins to bind and become activated. True/False
True. This action kicks off signal transduction pathways
Example of use of GPCR
Smell and taste signaling (Ca+ or Na+ channels)
Example of GPCR is epinephrine
Examples of use of Receptor Tyrosine Kinases(RTKs)
Some RTKs regulate basic cell division like
- Triggering cell division (stem cells)
- Differentiation of cell into different cell types
- Survival of cell: if it goes into the apopthesis(cell suicide) or not.
Function of RTKs
They trigger cell division and ‘guide’ what type of cell the divided cell will differentiate into.
Ligand-gated Ion channel receptors
When the ligand come into contact with the Ligand-gated Ion channel receptors, the gate open for the ions. These lets the ions inside (down their concentration gradient), when the ligand leaves the gate closes.
The ions don’t activate signal transduction. True/ False
False
Example of use for Ligand-gated Ion Channel Receptors
This happens a lot in neurotransmission
Transcription Factors
These are proteins that binds to DNA at specific nucleotides. Depending on what the body needs they turn ON or OFF the transcription of specific genes
Some ligand cross the plasma membrane. True / False
True. An example is steroid
Phosphorylation Cascades : process of transduction
A relay molecule activate the protein kinase(enzyme) by adding a phosphate. This goes on until a cellular response is made
Protein phosphates remove the phosphates from the cellular response. True/ False
True. All kinases and everything is shut off
Secondary Messengers
These are inside the cell. They either trigger other transduction processes, or directly trigger cellular response
Examples of Secondary Messengers
Calcium Ions
Cyclic AMP
Cyclic AMP
They are made by ATP. An enzyme called adenylyl cyclase converts ATP into cAMP
Phosphodiesterase
This breaks the ring of cAMP and turn it into adenosine monophosphate (AMP).
Advantage of having a multi-step transduction
This allows for greater control of how ‘big’ the signal output will be. Amplification of signal
Different cell types respond/interact to signaling differently
rapid signaling from dilute hormones
What are the types of signaling
Autocrine
Endocrine
Synaptic
Paracrine
Signal through cell-cell contact
Endocrine Signaling
This happens in the bloodstream. It occurs over long distance between hormone producing molecules. Often from the brain.
Paracrine Signaling
Occurs between cell in close proximity with each other.
Synaptic Signaling
Under paracrine signaling. Nerve cells transmit signals. the synapse, the junction between two nerve cells where signal transmission occurs.
Autocrine Signaling
A cell signals to itself. it releases a ligand that binds to the receptor on its surface
Signal through cell-cell contact
Gap junction are channels that directly connect neighboring cells
Crosstalk
The activation of relay molecule(transduction pathway) can influence or inhibit the response of other transduction pathways
The different signaling pathways that could happen when a ligand binds to a receptor
The normal pathways: signaling molecule -> receptor -> relay molecules - > Response
Signaling Molecule -> Receptor -> different Relay Molecule -> different responses
Crosstalk: two different ligand -> two different receptors -> two different relay molecules that affect each other(increase or inhibit) -> response
same Ligand -> different receptor - > different relay molecules ->Response
